为什么 String.protoptype.charCodeAt() 可以将二进制字符串转换为 Uint8Array？

Question

假设我有一个base64编码的字符串，我想把它转换成一个ArrayBuffer，我可以这样做：

// base64 decode the string to get the binary data
const binaryString = window.atob(base64EncodedString);

// convert from a binary string to an ArrayBuffer
const buf = new ArrayBuffer(binaryString.length);
const bufView = new Uint8Array(buf);   
for (let i = 0, strLen = binaryString.length; i < strLen; i++) {
    bufView[i] = binaryString.charCodeAt(i);
}

// get ArrayBuffer: `buf`

从String.protoptype.charCodeAt(), it will return an integer between 0 and 65535 representing the UTF-16 code unit at the given index. But an Uint8Array开始的范围值为[0, 255]。

我最初认为我们从 charCodeAt() 获得的代码点可能会超出 Uint8Array 范围的范围。然后我查看了内置的atob() function, which returns an ASCII string containing decoded data. According to Binary Array，ASCII字符串的范围是0到127，包含在Uint8Array的范围内，所以我们可以安全地使用charCodeAt()这种情况。

这是我的理解。我不确定我是否正确解释了这一点。感谢您的帮助！

Answer 1

看来我的理解是正确的。

感谢@Konrad，这里是 his/her add-up:

charCodeAt is designed to support utf-16. And utf-16 was designed to be compatible with ASCII so the first 256 characters have exact values like in ASCII encoding.

为什么 String.protoptype.charCodeAt() 可以将二进制字符串转换为 Uint8Array？

Why String.protoptype.charCodeAt() can convert binary string into an Uint8Array?

javascript

utf

character-encoding

typed-arrays